css de un pop up simple

style.css

.fadebox{
	display: none;
	position: absolute;
	top: 0%;
	left: 0%;
	width: 100%;
	height: 100%;
	background-color: black;
	z-index:1001;
	-moz-opacity: 0.8;
	opacity:.80;
	filter: alpha(opacity=80);
}

.overbox{
	width: 350px;
	margin-left: -175px;
	
	height: 350px;
	margin-top: -175px;
	
	position: absolute;
	display: none;
	top: 50%;
	left: 50%;
	
	z-index:1005;
	overflow: auto;
	background: white;
	padding: 20px 55px;
	
	-webkit-border-radius: 10px;
	-webkit-border-radius: 10px;
	-moz-border-radius: 10px;
	-moz-border-radius: 10px;
	border-radius: 10px;
	border-radius: 10px;
}